I don't know what might be the best but here is what I use. I have a fast action 9'6" 5wt Sage. I like the faster action so when I use weighted flies or split shot it doesn't slow the action too much. I like to tip flip mend and I find the faster action works best for that. I also use a GPX line. When I replace that line I am going to try the Nymph line from RIO. The longer rod gives me a lot of up stream mend with a reach cast. I also feel that I get a quicker hook set with the stiffer rod.

I am sure others have a system that works for them with slower action rods but I like my setup.